An Holley Terminator X Max Gen IV LS kit laid out on a plain white background, including multiple black coiled wires, connectors, a rectangular control module, small hardware pieces, and a metal probe wire.
A black Holley 550-918 Terminator X Max electronic control module with multiple connector ports and a blue wire, shown on a plain white background.
A pair of Terminator X Max 58x 4x EV6 harness electrical sensor connectors with attached black cables, shown on a plain white background. One connector has a clear plastic cap, and both have black multi-pin plugs with orange accent rings.
Black Terminator X MAX electronic control module shown from the front and back on a white background, with a blue connector wire visible.
A black Holley LS 4L60E 4L80E transmission control with multiple electrical connectors and a blue wire, shown on a plain white background.
A coiled black automotive wiring harness for Terminator X Max for 5.3 6.0 LS engine with multiple connectors, including a blue-painted terminal and white label bands, photographed on a plain white background.
Black braided Holley Terminator X Max wiring harness with a multi-pin connector, shown with three small clear plastic connector tips on a white background.
A terminator X Max wiring harness with a black multi-pin connector on one end and a black wire tie on the other, shown on a white background.
An Holley Terminator X Max Gen IV LS kit laid out on a plain white background, including multiple black coiled wires, connectors, a rectangular control module, small hardware pieces, and a metal probe wire.
A black Holley 550-918 Terminator X Max electronic control module with multiple connector ports and a blue wire, shown on a plain white background.
A pair of Terminator X Max 58x 4x EV6 harness electrical sensor connectors with attached black cables, shown on a plain white background. One connector has a clear plastic cap, and both have black multi-pin plugs with orange accent rings.
Black Terminator X MAX electronic control module shown from the front and back on a white background, with a blue connector wire visible.
A black Holley LS 4L60E 4L80E transmission control with multiple electrical connectors and a blue wire, shown on a plain white background.
A coiled black automotive wiring harness for Terminator X Max for 5.3 6.0 LS engine with multiple connectors, including a blue-painted terminal and white label bands, photographed on a plain white background.
Black braided Holley Terminator X Max wiring harness with a multi-pin connector, shown with three small clear plastic connector tips on a white background.
A terminator X Max wiring harness with a black multi-pin connector on one end and a black wire tie on the other, shown on a white background.

Holley EFI Terminator X Max for Gen IV GM LS Engines – 58x/4x, EV6, 4L60E/4L80E Control

550-918

$1,999.95
/
Shipping calculated at checkout.

The Holley EFI Terminator X Max for Gen IV GM LS Engines – 58x/4x, EV6, 4L60E/4L80E Control gives builders complete control over compatible GM LS truck engines, LS2, and LS3 combinations without relying on a modified factory ECU. This system combines self-learning fuel control, ignition timing control, wideband oxygen sensing, programmable inputs and outputs, data logging, and electronic transmission control in one compact package.

Designed for Gen IV LS engines using a 58x crank reluctor, 4x cam signal, USCAR/EV6 injectors, and cable-operated throttle bodies, the Terminator X Max supports 4L60E and 4L80E electronic transmissions. Choose PN 550-918 with the 3.5" touchscreen handheld or PN 550-918T without the handheld for installations using a laptop or compatible Holley display.

Includes:

  • (1) Holley Terminator X Max ECU
  • 58x/4x GM LS Engine Main Harness
  • USCAR/EV6 Injector Harness
  • 4L60E/4L80E Transmission Control Harness
  • ECU Main Power Harness
  • Bosch LSU 4.9 Wideband Oxygen Sensor
  • Input/Output Harness
  • MAP Sensor Vacuum Hose Adapters
  • 3.5" Touchscreen Handheld with PN 550-918 Only
  • Fuel System Components, Injectors, Throttle Body, and Mounting Hardware Not Included
Specifications
Specification Details
Manufacturer Holley EFI
Part Numbers 550-918 With Handheld / 550-918T Without Handheld
Product Type Self-Tuning EFI and Transmission Control System
Engine Family Gen IV GM LS
Crank Reluctor 58x
Cam Signal 4x
Ignition Type GM LS 58x Coil-Per-Cylinder
Injector Connector USCAR / EV6
Injector Driver Type High Impedance
Transmission Control 4L60E / 4L80E
Drive-By-Wire Support No
Wideband Oxygen Sensor Bosch LSU 4.9
Internal MAP Sensor 1 Bar
Programmable Inputs 4
Programmable Outputs 4
Boost Control Yes
Nitrous Control Wet or Dry, Progressive or Non-Progressive
E85 Support Yes
Data Logging Yes
CAN-BUS Support Yes
Finish Black Textured
Fitment
Engine Application Compatibility
294 / 4.8L V8 Compatible with 58x Crank, 4x Cam, and EV6 Injectors
325 / 5.3L V8 Compatible with 58x Crank, 4x Cam, and EV6 Injectors
346 / 5.7L V8 Compatible with 58x Crank, 4x Cam, and EV6 Injectors
364 / 6.0L V8 Compatible with 58x Crank, 4x Cam, and EV6 Injectors
376 / 6.2L V8 Compatible with LS2/LS3-Based 58x/4x Applications
427 / 7.0L V8 Compatible with Proper 58x/4x and EV6 Configuration
Electronic Transmission 4L60E or 4L80E
Throttle Control Cable-Operated Throttle Body

Fitment Notes

  • Designed for Gen IV GM LS engines with a 58x crank reluctor and 4x cam signal.
  • Requires high-impedance injectors with USCAR/EV6 connectors.
  • Will not control low-impedance fuel injectors.
  • Designed for cable-operated throttle bodies and does not support drive-by-wire throttle control.
  • Transmission control is provided for compatible 4L60E and 4L80E transmissions.
  • Not compatible with 4L6X transmissions from model year 1995 or earlier due to converter lockup and downshift strategy differences.
  • Not recommended for four-wheel-drive applications using an electronically controlled transfer case.
  • The internal 1-bar MAP sensor is intended for naturally aspirated or nitrous combinations.
  • Boosted applications requiring a 2-bar or higher MAP sensor can use GM PN 12592525 with Holley adapter PN 558-416.
  • The ECU is not recommended for marine use.
  • Off-road installations must keep the ECU dry, protected from heat, and mounted with the diagnostic LEDs facing upward.
  • Verify crank reluctor, cam signal, injector connector, throttle type, and transmission compatibility before ordering.
FAQ

1. What is the difference between PN 550-918 and PN 550-918T?

PN 550-918 includes the 3.5" touchscreen handheld, while PN 550-918T does not. Both versions include the Terminator X Max ECU, engine harness, transmission harness, wideband oxygen sensor, power harness, and supporting EFI wiring.

2. What does the self-learning feature do?

The ECU monitors air-fuel ratio through the Bosch LSU 4.9 wideband sensor and makes real-time corrections to the base fuel table. This helps establish a usable tune faster, but the installation still requires proper engine setup, sensor configuration, and verification.

3. Can this system control a 4L60E or 4L80E transmission?

Yes. The Terminator X Max includes electronic control for compatible 4L60E and 4L80E transmissions, allowing transmission functions to be configured through the Holley EFI software or handheld interface.

4. Can the Terminator X Max control a boosted or nitrous engine?

Yes. The ECU supports boost control, wet or dry nitrous, progressive nitrous control, boost and nitrous safeties, and advanced custom tables. Boosted combinations require a properly sized external MAP sensor because the internal sensor is limited to 1 bar.

5. What can the four inputs and four outputs be used for?

The programmable inputs can monitor switches, pressure sensors, nitrous activation, trans brake signals, and other triggers. The outputs can control relays and devices such as electric fans, boost solenoids, nitrous systems, warning lights, and compatible idle air control hardware.

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